Characterization and Application of a New β-Galactosidase Gal42 From Marine Bacterium Bacillus sp. BY02

Abstract

β-Galactosidase plays an important role in medicine and dairy industry. In this study, a new glycoside hydrolase family 42 (GH42) β-galactosidase-encoding gene, gal42, was cloned from a newly isolated marine bacterium Bacillus sp. BY02 and expressed in Escherichia coli. Structural characterization indicated that the encoding β-galactosidase, Gal42, is a homotrimer in solution, and homology modeling indicated that it retains the zinc binding sites of the Cys cluster. The reaction activity of Gal42 was significantly increased by Zn2+ (229.6%) and other divalent metal ions (Mn2+, Mg2+, and Co2+), while its activity was inhibited by EDTA (53.9%). Meanwhile, the thermo-stability of the Gal42 was also significantly enhanced by 5 and 10 mM of zinc ion supplement, which suggested that the “Cys-Zn” motif played important roles in both structural stability and catalytic function. Furthermore, Gal42 showed effective lactose hydrolysis activity, which makes the enzyme hydrolyze the lactose in milk effectively. These properties make Gal42 a potential candidate in food technology.

Immobilization of Lactobacillus acidophilus β-galactosidase on chitosan obtained from the shells of the African giant snail, Achatina achatina

“…The LacLM heterodimeric Lactobacillus acidophilus R22 β-galactosidase was activated by Mg 2+ which improved both activity and stability suggesting the possible presence of binding sites for Mg 2+ within the active site which might interact with Glu residues and, thus, could contribute to both subunit interactions and global enzyme stabilization. 9,46 Chitin is insoluble in water and organic solvents but could be processed by extensive alkaline deacetylation to obtain a more soluble product called chitosan. The chitin yield from the Achatina shells was 74.64%, while the chitosan yield was 58.60%.…”

Covalent immobilization of β-galactosidase using a novel carrier alginate/tea waste: statistical optimization of beads modification and reusability

“…The activity of β-gal can be estimated by liberating O-nitrophenol (ONP) from O-nitrophenyl-β-D-galactopyranoside (ONPG) as a substrate according to the method characterized by Zhou et al [ 22 ] with some modifications. The reaction was started by adding 0.1 ml of the enzyme solution (in the case of a free enzyme) or 0.1 g of beads (in the case of an immobilized enzyme) to 0.9 ml of 10 mM ONPG solution prepared in phosphate buffer (0.1 M, pH 7.0).…”